1. Field Of The Invention
This invention concerns an engine timed ignition system in general. More specifically, it deals with an improved system that makes use of a short duration high voltage spark plus a reduced voltage DC spark sustaining signal.
2. Description of The Prior Art
In an engine timed ignition system, it has been suggested that the conventional short time high voltage spark signal might be supplemented with a lower voltage DC signal that is applied so as to continue the spark discharge for some time thereafter. Two patents which describe ways of carrying out the foregoing suggestion are (1) the U.S. Pat. to Birchenough, No. 4,033,316, issued July 5, 1977, and (2) the patent to Shimojo et al, No. 4,136,301, issued Jan. 23, 1979.
The Birchenough patent provides for creating a conventional inductive discharge type high voltage signal to create the spark which develops at the sparkplug of an internal combustion engine. And, the application of a DC voltage that has sufficient amplitude to keep the spark from being extinguished thereafter. However, in the system which Birchenough discloses, there is a difficulty in connection with the spark discharge continuing beyond the need therefor at each cylinder of the engine. Thus, even though the spark discharge was supposed to be extinguished by the engine's operational cycle in reliance upon the exhaust, intake or compression in the cylinder, it was not found to be effective in extinguishing the spark discharge. Similarly, whereas Birchenough suggested that the distributor rotor would break the current path to each cylinder, it has been found that a damaging discharge would continue unabated.
In contrast, the applicants' system positively cuts off the DC sustaining voltage at the end of a predetermined time interval so that the next spark discharge can be controlled and regulated, in a similar manner for each cylinder of the engine.
In the Shimojo et al patent, the same type of problem was recognized, and it attempts to overcome the difficulty by having its DC to DC converter connected so as to be developing an auxiliary or sustaining DC signal prior to the introduction of the spark initiating signal. It includes a feedback arrangement in the DC to DC converter to control the current supply and so permit the spark to be extinguished when the pressure in a cylinder increases. Consequently, the system of Shimojo et al does not start the two signals simultaneously, nor does it act to stop the oscillator of the DC to DC converter when the spark termination is desired.
Thus, it is an object of this invention to provide an improved system for using an engine timed ignition signal that includes a short duration high voltage spark initiating signal, plus a reduced voltage DC spark sustaining signal which latter is commenced simultaneously with the initiating signal and is positively stopped after a predetermined time interval.